Qinghai Lake is an acid lake and located in Tengchong County, Yunnan province.Qinghai Lake is a crater lake with continuously acid groundwater supply, which is the geological foundation of the acid lake.We analyzed water, soil, sediment and biological samples of Qinghai Lake.As result showing, the water has low pH value, very low cation concentration and mineralization degree, and obviously migration of element Ca, Mg, Al and Fe in sediment.Few species, low biomass and lack of blue-green algae, Gastropoda, Lamellibranchia and Crustacea are most notable characteristics distinguished from general neutral and alkaline lakes.Change of element geochemistry behavior of acid aqueous medium in a lake, and its impact on organisms cause the decrease of acid sensitive species and the increase of acid tolerant species, these are the basic characteristics of Qinghai Lake and dynamic mechanism of forming acid lake environment.